Original diagrams from Gray's anatomy, now out of copyright. These diagrams have been reproduced from Gray's Anatomy 20th US edition which has now lapsed into the public domain
- https://commons.wikimedia.org/wiki/File:Gray149.png
- https://commons.wikimedia.org/wiki/File:Gray150.png
- https://commons.wikimedia.org/wiki/File:Gray151.png
- https://commons.wikimedia.org/wiki/File:Gray152.png